Safety switch



May 17, 1949. L. JAcoBs 2,470,701

SAFETY SWITCH v Filed Aug. 29, 1947 2 Sheets-Sheet 1 ,l "uw ML I i lf2 j f E' .j j IN1/EN TOR.

May 17, 1949.

Filed Aug. 29. 1947 L. JACOBS SAFETY SWITCH 2 Sheets-Sheet 2 INVENTOR. lf-@NARN hangs A TTR/VEX Patented May 17, 1949 SAFETY SWITCH :Leonard tJacobs, slPhiladelphia, rPa., assigner v to iRadio-Gorpotation of America, `a corporation oflDelaware V"Aplr'lication""AugustJ29, 1947,: Serial N0."771;321

(Cl. ZOO-54) Ttolconventinaltsafetyesystems and to providean 1linother-andfimportantobject of fthe invention The invention will ybe. described .in connection with the acdmpaying:'drawings," wherein:

iris-an side-elevational. view,ipa'rtly in. section of a safety system including. a-:three'fposition door switch constructed `in.accordance with the invention;"the"dbor and "the switch being closed. f

Figs22 is a similar views-.with the door-open ligand the switch contacts open.

"Figi 3 is'aview similar toFig; 2, with the door fipenbut'fwith-the switch-movedto a third posii'fin wherat its contacts are? closed.

Fig. 4 is a side elevational View, Apartly in section for installation similar to the one shown in Figs. 1-3 but wherein the switch contacts are biased to open when the door is opened and,

Fig. 5 is a side elevational View, partly in section, showing the invention as applied to an installation employing a conventional microswitch.

In the embodiment of the invention shown in Figs. 1, 2 and 3, I designates the door, or hinged lid and 2 the front panel of a compartment 3 which may contain, in addition to a switch 4, the high voltage apparatus (not shown) which the switch is designed to control. The switch 4 is shown mounted within the compartment upon a lior-#preventingh access7 tothe chassis or shelf t5 which' extends Vrearwardly," from Ythe irontpanelx2. .In:.the=instant case theiswitch :comprises .two sets:of;parallellyi arrangedaswiteh llarms I5-JI, 849; whicha are. constituted .oi spring .zmetal yand areasupported adiacentito: their armer ends `.upon an,` insulating pedestalp. 'eEach larm isf-providedwith aswitch contact-16031@ 8c, Bere- .spectivelygin register-with the contact .witlrwhich afitispaired. Since all ofthe-switch amiss-esatte constituted of spring material and eachfarmcis :mounted .in spaced. relation-with respect `tothe particularl arm with-wlciich.it.isy paired, :it will vbe apparent'that all ofthe contactarse-9c arenormally biased to theirfopenl position (shownin Fig. 2)` by the spring-actionfof their said supporting arms. One armY of eachpair (inthis case the ffinner. aims "I an'df) extends `beyondI the free iend of theother-farmsand the tree rends .of these longer arms yterminate ina preferably Ioutward-ly inclined U-shaped section flu;` 8uj-to whiclra force may be applied in ardire'ctionfcalculated:to vclose the contacts f lic-'10;' llc-#9al against"v the .biasing forceA of -the resilient'.material.ofl which the switch farms 6 9 are formed.

The vforce required -to. close the switch contacts 6c`1c etc. against ithelbiasf of `the-switcharms 6,'1' etc.;- is supplied by'closing the 'door andcis applied. to the -U-"shapeterminals'A 'lu-A and. 8u -of the arms- 'Ily and-i 8 throughhalplunger mechanism, @indicated Igenerally Yat #I IIL-f which extends through a bushing Il surrounding an aperture I-Ia in the @shelf iandpan'el' 2. "TheHplunger'mechanism itself comprises yah'ollew insulating sleeve I2 which has a'sliding tin theA bearing II andan yinner rod-like1fniemherrv I3-fwhich fhas a-si-milar lt in the bore of the sleeve I2. Theouter end*- of vthe rod I 3-terminates-in knob 13k which is-biased outwardly to bearag'ainst'fthel-doorkv 2, wherrthe 1` doors closedgfbyal coil spring `I4-whichis seated 4-`within the-sleeve-IZ. Afpin -15 limits lthe-extent of the outward movement ofithe rod 1I 3v within the sleeve I2. When the door I is closed the knob I3k is received in a counter-bore l Ir in the front panel so that the outer plane surface of the knob I3lc lies flush with the inner surface of the door. The sleeve I2 of the plunger mechanism is provided adjacent to its inner end with an outwardly inclined surface I2a against which the bent ends 7u, 8u, 'of the spring arms I and 8 oi the switch are adapted to bear, when the door is closed. The said arms 'I and 8 thus exert an outwardly directed axial force on the sleeve I2 in a direction opposite to the holding force exerted thereon by the door when it is closed. Thus, when the door is opened the energy stored aatofi in me resiiient arms 1 and a is translated by the inclined surface I2a of the sleeve into an outwardly directed axial force which causes the sleeve I2 to move to the right a limited distance sucient to break the engagement between the contacts lic-1c and 8c-9c. With the door opened the energy of the coil spring I4 within lthe sleeve I2 is also released and serves to move the knob I3k out of its' recess IIT to a position (shown in Fig. 2) whereat it may be grasped for the purpose of re-setting the ycontacts while the door is open.

The novel form of the inner end of the sleeve I2 of the plunger permits the switch contacts (ic-'Ic etc. to be closed and maintained in the closed position while the door is open. This terminal section of the sleeve comprises, in addition to the inclined surface IZa, a. riser I2C on the end of the sleeve and a dwell or cut-away portion I 2b intermediate the riser I2C and the inclined surface I2a. As shown in Fig. 2 the diameter of the dwell lib is suiiiciently small to permit the contacts 6c, 'Ic etc. to stay open so long as the bent-ends 1u, 8u of the switch arms 1 and 8 remain therein, whereas the diameter of the end DOIOH I2C adjacent to the dwell is sufliciently large to close the said contacts when the sleeve is pulled o-ut of the position, shown in Fig. 3, whereat the bent ends 1u, 8u of the switch arms rest thereon.

The switch is automatically re-set from either of its above described open or closed positions since in moving the door to its closed position, the knob I3lc is urged inwardly against the force of the coil spring I4 until the said knob abuts the sleeve I 2 which is then moved inwardly until, when the door is tightly closed, the ends of the switch arms 1u and 8u come to rest upon the inclined surface I2a of the sleeve.

In certain installations (e. g. in dark enclosures wherein the door switch operates to turn on a light when the door is opened, and wherein it may be desired to turn-oli the light while the door is open) the switch arms may be arranged to open when the plunger is in and to close when the plunger is Dartway out. One way of achieving this in a switch of the general character shown in Figs. 1 to 3 is to reverse the position of the shorter arms 6 and 9 so that, as shown in Fig. 4, the conta-cts Se, Ic etc. are normally biased to their closed position.

In the door-actuated switch installation shown in Fig. 5, the switch, which is here designated 20, comprises a conventional micro-switch wherein the actuating arm 2| is normally biased to its extended position. Here the door actuated plunger of the invention comprises simply a solid metal rod 22 mounted for slideable movement along an axis normal to the axis of movement of the arm 2I and having an intermediate portion or dwell 22h of reduced diameter in which the said arm is adapted to be accommodated when the door is opened. In the instant case, the energy required to move the plunger to a position whereat the dwell I2b is in register with the switch arm 2 I is provided by a coil spring 23 about the inner end of the plunger. This spring 23 is under compression when the door is closed but is not rigidly affixed to the plunger and hence does not prevent the plunger from -being pulled out, when the door is open, to a position whereat the switch arm is in its illustrated closed posi-- tion.

It will now be apparent that the present invention provides an improved door-actuated safety system and switch and one wherein the switch may be set while the door is open and automatically re-set from either its closed or its open position upon closing the door.

What is claimed is:

1. In apparatus of the character described, a switch having an actuating arm, a plunger mounted for axial movement along a line which intersects the line of movement of said arm, said plunger having an intermediate dwell-portion of reduced diameter, equal diameter end portions, and switch positions corresponding to said portions, said arm being biased into Contact with said plunger, and a coil spring associated with said plunger biasing said plunger from one of said end positions to said intermediate position, said spring being inoperative when said plunger is in its other end position.

2. In apparatus of the character described, a plunger mounted for axial movement, said plunger having an intermediate dwell portion of a diameter less than either of its end portions and having three switch positions corresponding to said portions, a switch having an actuating arm mounted in register with said dwell portion when said plunger is in its intermediate position, said arm being biased into continual contact with said plunger, and resilient means associated with said plunger biasing said plunger to its intermediate position when said plunger is moved in one direction from its intermediate position, said biasing means being inoperative when said plunger is moved in the opposite direction from its intermediate position.

LEONARD JACOBS.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 292,687 Scott Jan. 29, 1884 1,038,776 McLarn Sept. 17, 1912 2,079,252 Healy May 4, 1937 2,122,643 Golemb July 5, 1938 

